heneghan, still air distances don't translate into ground distance. A 100kt headwind westbound means a tech stop for fuel. Globespan usually tech stopped on the westbound whenever they used the 737. Pax don't like looking out the window at Gander or St Johns for an hour.
Also, as I mentioned above, a 737NG cannot take off at MTOW from Knock on days with low atmospheric pressure (i.e. winter) as the runway isn't long enough.